Inkjet recording is a recording system for forming characters or images, comprising directly jetting ink droplets from very fine nozzles to a recording medium, and depositing the ink droplets on the recording medium. This system has some advantages such that not only does the device show excellent operability at a low level of noise, but also the coloration is facilitated and a plain sheet of paper can be used as a recording medium. Therefore, this system has been recently widely used. Especially, the inkjet recording system has advantages in full-color recording techniques such that vivid images having high chroma can be obtained as compared to other recording systems when dyes rich in color tones are used.
Since light-fastness, water resistance and the like are required for an ink used for an inkjet printer, a pigment dispersion has been recently used as a colorant.
In a pigment dispersion which has been used as a writing utensil or general ink, a polymer dispersant, a surfactant or the like has been used. However, when this pigment dispersion is used for a water-based ink for inkjet recording, optical density of a printout is unsatisfactory, and jetting ability or the like of the ink droplet is unsatisfactory.
In order to eliminate this advantage, there has been proposed an ink containing an anionic polymer dispersant made of a copolymer having an aromatic ring, a carboxylate and a long-chain alkyl carboxylate group, an aqueous medium and a pigment as disclosed in Japanese Patent Gazette No. 3056664.
However, there are some advantages in this ink such that storage stability of the ink and water resistance of the printout are unsatisfactory.